1040 Environmental Toxicology and Chemistry, Vol. 26, No. 5, pp. 1040–1046, 2007  2007 SETAC Printed in the USA 0730-7268/07 $12.00 + .00 DEER EXPOSED TO EXCEPTIONALLY HIGH CONCENTRATIONS OF LEAD NEAR THE CONTINENTAL MINE IN IDAHO, USA W. NELSON BEYER,*† GREG GASTON,‡ ROY BRAZZLE,‡ ALLAN F. O’CONNELL,JR.,† and DAN J. AUDET§ †U.S. Geological Survey, Patuxent Wildlife Research Center, BARC East, Building 308, 10300 Baltimore Avenue, Beltsville, Maryland 20705 ‡U.S. Fish and Wildlife Service, Upper Columbia Fish and Wildlife Service Office, 11103 East Montgomery Drive, Spokane, Washington 99206 §National Park Service, 1103 North Fancher Road, Spokane, Washington, USA ( Received 16 June 2006; Accepted 30 November 2006) Abstract—Habitat surrounding the inactive Continental Mine in northern Idaho, USA, supports bear (Ursus arctos, Ursus amer- icanus), moose (Alces alces), elk (Cervus elaphus), woodland caribou (Rangifer tarandus caribou), and abundant mule (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus). Tailings on the mining site were capped and remediated in 2003 to reduce environmental exposure of surrounding soil and sediments of Blue Joe Creek, downslope of the mine. Before capping, the mean Pb concentration in deer pellets collected on-site was 920 mg/kg of Pb (dry wt). This exposure, if chronic, would be comparable to an exposure that could be lethal to cattle or horses. Surprisingly, the mean pellet Pb concentration of 950 mg/kg in 2004 was as high as it was before remediation, and it was related to a high rate of soil ingestion. Mean soil content of the pellets collected from the capped site in 2004 was 22% dry weight, estimated from the acid-insoluble ash, a marker of soil ingestion. Clumps of sand and bits of rock were observed inside some of the pellets, and Pb concentrations in the pellets were correlated (p  0.05) with soil content. Although terrestrial risk assessments generally estimate exposure from diets and from incidentally ingested soil, the deer at this site were directly ingesting contaminated soil or mining waste. The mean Pb concentration of this ingested soil was estimated as 6,700 mg/kg and the maximum as 25,000 mg/kg, well above the Pb concentrations measured in the remediated cap. The deer seemed to be ingesting soil or mining waste from one or more small but highly contaminated sources located beyond the remediated cap. Keywords—Lead Deer Mining Tailings Exposure INTRODUCTION The Continental Mine is located in the Selkirk Mountains, about 9 km south of the Canadian border in the Idaho pan- handle, USA. The mine is within a grizzly bear recovery zone and is at the southern end of the range of the Selkirk population of the endangered woodland caribou (Rangifer tarandus car- ibou) [1]. The surrounding habitat also supports deer, moose, and elk. Tailings from this now-inactive Pb mine contaminated nearby soils and sediments with Pb and associated metals. The 6-ha mining property was remediated in 2003 (Herrerra En- vironmental Consultants, 2004, Removal Action Report. Con- tinental Mine, Boundary County, Idaho, TDD 03-01-0005, Seattle, WA, USA) under an emergency removal action by the U.S. Environmental Protection Agency (U.S. EPA) to reduce human and ecological exposure to Pb. Because mule deer and white-tailed deer play an important ecological role in these high-elevation habitats and are valued by the public, we se- lected them for evaluating the hazards to wildlife associated with the contamination. Deer pellets were collected before (2003) and after (2004) the remediation to evaluate exposure to Pb at the site and the effectiveness of the remediation. Analyses of feces provide a useful measure of exposure to contaminants [2–5], especially to elements such as Pb that are poorly absorbed from an animal’s gut. Based on studies of Pb poisoning in humans [6], domestic animals [7,8], and wildlife [9,10], we expected that if the deer ingested substantial amounts of Pb, most of that Pb would be associated with * To whom correspondence may be addressed (nbeyer@usgs.gov). ingested soil or sediment. The amount of soil or sediment in feces may be estimated from the acid-insoluble ash of a sample or from the concentration of a marker in soil, such as Al [11]. The two measures may differ since Al is more closely asso- ciated with fine than with coarse soil particles. If the Pb in sampled pellets is assumed to come primarily from soil in- gestion, then the Pb concentration of that ingested soil may be estimated from the amount of soil ingested and from the Pb concentration in that sample. Identifying the sources of Pb to deer, however, is complicated by their movement. The mean retention time of a diet is roughly 23 h in white-tailed deer and 46 to 63 h in mule deer [12], and typical home ranges are estimated as 2.6 km 2 for white-tailed deer [13] and 0.4 to 1 km 2 for mule deer in mountainous areas [14]. Both species tend to move less in July and August, when the samples were collected. We did not try to differentiate pellets of mule deer from the less abundant white-tailed deer. MATERIALS AND METHODS The Continental Mine is on a steep, southeastern, slope at an elevation of about 1,700 m. The surrounding forest is a Picea-Abies mix, with an undergrowth of false huckleberry (Menziesia ferruginea) or common bear grass Xerophyllum tenax [15]. The habitat downslope, which borders Blue Joe Creek, is closer to Daubenmire’s [15] description of a Thuja- Tsuga/Oplopanax habitat. The mine’s red vein, mainly galena, was discovered first and is about a kilometer long and has a strike of 40° east of north [16]. The black vein, similar in attitude and minerali-